STABILIZATION AND MODIFICATION OF POLYCAPROAMIDE - Photochemical Reactions in Heterochain Polymers - page 22

Photographs of dyed and undyed fibres and their cross-sections at 20-times increase,
where homogeneity of polymer structure is distinct, show good solubility of bis-
aroilenbenzimidazole derivatives in PCA melt. It should be noted that the process of fibres
formation, containing XL-XLVI dyes, went on steadily and there were no difficulties during
extraction.
Figure 1.3 present spectra of XLV dye solution absorbtion in the mixture of formic and
trifluoro-acetic acids, solutions of dyed fibres before and after spinneret, which are practically
laid on each other, showing full solution of the dye and good homogeneization of polymer
melt. It should be noted that the samples of fibres, being studied, fully dissolved in solvents
without formation of residues (possible products of dye and PCA interaction), which tells
about inertia of components regarding each other. Blinding screen was caused mainly by
impurities of mechanical nature.
Besides, tests on possibility of XL-XLYI compounds use for mass dyeing of PCA
through the stage of obtaining polymeric concentrate of the dye (PCA).
In the process of polyamidation foaming of the polymer was not observed. Thermal
stability of the dyes is satisfactory at warming - up for 48 hours and this shows that their
introduction at the stage of ε - caprolactam polyamidation does not deteriorate PCA
properties.
Data, given in Table 3, show that small amounts of the dye (up to 2% of mass) do not
exert essential effect on molecular weight of polymer. It should be noted that polymer gains
bright colour even at dye concentration of 1% of mass.
Table 3. Molecular weight of synthesized PCA, dyed by XLY compound through the
stage of polymeric concentration of the dye

Number Polymer sample Additive concentration η Molecular weight

1. Initial PCD 0 0,61 18000

2. PCD+XLY dye 0,25 0,62 18600

3. -//- 0,50 0,61 18000

4. -//- 1,00 0,59 17500

5. -//- 2,00 0,60 17800

6. -//- 5,00 0,45 12000

Thus, all compounds, being tested, dissolve and combine with PCA melt quite well and
do not influence the polymer negatively. On the other hand, these dyes are stable in polymer
melt.

1.2. P HOTOOXIDATIVE D ESTRUCTION OF D YED PCA

Breaks of the main chain of macromolecules are the main reasons for the loss of PCA
service properties at photooxidative destruction; therefore definition of the change of polymer
molecular weight before and after photooxidation is one of the methods of evaluating such
important characteristic as the number of breaks. There were investigated PCA samples